AMF, midsummer orchard management

By Terence Bradshaw

Despite localized rains early this week, it’s still really dry out there. That means running irrigation if you can, and considering what it will take to get it in the future because I expect we’ll be seeing more of these extreme dry summers. That also means that summer diseases haven’t been much of a concern. But wet weather is expected for next week and may be enough to trigger infection of sooty blotch/flyspeck or summer rots. It may be worth thinking about your (first?) summer fungicide in the next week or so.

While you’re thinking about coverage in the orchard, the main target to consider should be apple maggot (AMF). We’ve seen very high numbers in virtually all monitored orchards in Vermont and colleagues to the east, west, and south (and I wouldn’t be surprised about the north) are saying the same thing. Of course, use trap catches on your farm to guide management of this pest, but I expect that many will be treating (and maybe re-treating). Codling moth (CM) remains between generations for all Vermont orchards, and applications aimed at AMF, as long as the material has some efficacy against CM, will take care of any stragglers. CM trap captures are high in most monitored orchards would plan to treat with a CM-specific material like Rimon, Intrepid, Delegate, granulosis virus, or other material with high activity against lepidopterans (except Bt, which isn’t very effective against CM) in the next 7-14 days. Check NEWA for insect model development.

Horticulture: add calcium in every spray, the lack of water will certainly be minimizing uptake from the soil. If you haven’t yet, consider applying potassium fertilizers based on foliar or soil analysis (foliar preferred). If you don’t have a previous foliar analysis, figure on a rate of 50 lbs actual potassium per acre as a rule of thumb.

On the topic of foliar nutrient analysis – It is the time in the growing season to collect leaf samples for analysis. Samples are usually collected between July 15 – Aug. 15. The UVM Agriculture and Environmental Testing Lab can provide analysis, but at this time their output does not generate fertility recommendations. The following are potential options of labs for analysis. It is recommended that you contact the lab for instructions and costs before samples are sent. Plus, it is important to confirm that they will send recommendations along with the analysis.

(1) University of Maine Analytical Lab:
(2) University of Massachusetts Soil and Tissue Testing Lab:
(3) Cornell Nutrient Analysis Lab:

Finally, terminal buds have set on most trees so you can think about summer pruning any time. Remember, you’re only looking to get some light into the canopy and onto fruit, not to reshape the tree. Judicious trimming mostly of this year’s watersprouts is most all that you’ll need. I tell my help to spend no more than 1-2 minutes on an M7 tree.

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